In semiconductor manufacturing processes, a process for implanting ions into a semiconductor wafer is performed in a standard procedure for the purpose of varying conductivity, varying a crystalline structure of the wafer, or the like. An apparatus used in this process is called an ion implantation apparatus. The ion implantation apparatus has a function of generating ions using an ion source, and then forming an accelerated ion beam, and a function of irradiating the entire surface of the semiconductor wafer with the ion beam, through beam scanning, wafer scanning, or a combination thereof.
In the semiconductor manufacturing processes, in order to create semiconductor chips having the same performance across the entire surface of the wafer, typically, it is necessary to form a uniform condition in the wafer surface, in the ion implantation process, typically, the ion implantation apparatus is controlled such that an ion implantation amount implanted over the entire region of the wafer is made to be uniform.
In some semiconductor manufacturing processes, it is difficult to obtain uniform conditions in the wafer surface in principle, particularly, in recent years, miniaturization of the semiconductor chip has rapidly progressed, and as the difficulty in obtaining uniform conditions in the wafer surface has increased, the extent of non-uniformity also increases, if a uniform condition is formed in the wafer surface in other processes under such conditions, as a result, semiconductor chips having the same performance in the entire wafer surface cannot be created. For example, in the ion implantation process, when a typical ion implantation is performed for the entire region of the wafer such that an ion implantation amount in the surface is uniform, electrical characteristics of resultant semiconductor chips are not the seine as each other, and thus semiconductor chips having the same performance cannot be created.
Therefore, in a case where a uniform condition cannot be formed in the wafer surface in the other semiconductor manufacturing processes, in order to handle dose amount non-uniformity in the wafer surface, an intentional non-uniform two-dimensional ion implantation amount in-surface distribution (hereinafter, simply referred to as two-dimensional ion implantation amount in-surface distribution by omitting “intentional non-uniform” in some cases) may be created in the process of irradiating the entire wafer with an ion beam using the ion implantation apparatus, and the dose amount non-uniformity in the wafer surface may be corrected in the other semiconductor manufacturing processes. At this time it is important to employ an ion implantation apparatus and an ion implantation method having a function capable of handling both the size of the dose amount non-uniformity in the wafer surface and a two-dimensional non-uniform shape pattern thereof in the other semiconductor manufacturing processes.
As an example of the method of creating a two-dimensional ion implantation amount in-surface distribution in the wafer surface, there has been proposed a method of controlling a scanning speed by an ion beam and a scanning speed (mechanical scanning speed) by a semiconductor wafer (refer to Japanese Unexamined Patent Publication No, 2003-86530).
In an ion implantation method disclosed in Japanese Unexamined Patent Publication No. 2003-86530, only a scanning speed by an ion beam and a scanning speed by a semiconductor wafer are controlled. In this case, a control range of the scanning speed is restricted, and thereby a large-scale two-dimensional ion implantation amount in-surface distribution where a ratio of the maximum ion implantation amount to the minimum ion implantation amount in the wafer surface is five times or more cannot be realized.
In addition, since the ion implantation method disclosed in Japanese Unexamined Patent Publication No, 2003-86530 is aimed at creating regions having different ion implantation amounts on a wafer, patterns of ion implantation amounts which can be implemented in a wafer surface are restricted, and thus it does not have a function of creating a two-dimensional ion implantation amount in-surface distribution capable of handling a two-dimensional non-uniform shape pattern in other semiconductor manufacturing processes.
It is desirable to realize a two-dimensional ion implantation amount in-surface distribution where a ratio of the maximum ion implantation amount to the minimum ion implantation amount in the wafer surface is of a large scale.
Specific objects of the present invention are to realize the following.
1. To realize a large-scale two-dimensional ion implantation amount in-surface distribution where a ratio of the maximum ion implantation amount to the minimum ion implantation amount in the wafer surface is five times or more.
2. To provide a function capable of handling the degree of dose amount non-uniformity in a wafer surface in other semiconductor manufacturing processes.
3. To provide a function capable of handling a two-dimensional non-uniform shape pattern of dose amount non-uniformity in a wafer surface in other semiconductor manufacturing processes.
4. To control the function capable of handling the degree of dose amount non-uniformity in a wafer surface and the function capable of handling a two-dimensional non-uniform shape pattern independently from each other. For example, even if the degree of dose amount non-uniformity in a wafer surface is the same, a two-dimensional non-uniform shape pattern thereof can be varied, and, conversely, even if a two-dimensional non-uniform shape pattern is the same, the degree of dose amount non-uniformity in the wafer surface can be varied.
The present invention is applied to an apparatus which scans an ion beam in a beam scanning direction, mechanically scans a wafer in a direction substantially perpendicular to the beam scanning direction, and implants ions into the wafer.
According to an aspect of the present invention, an ion implantation method is provided, in the ion implantation method, an ion beam is scanned in a beam scanning direction and a wafer is mechanically scanned in a direction perpendicular to the beam scanning direction so as to implant ions into the wafer. The method comprises setting a wafer rotation angle with respect to the ion beam so as to be varied. A set angle of the wafer rotation angle is changed in a stepwise manner so as to implant ions into the wafer at each set angle. A wafer scanning region length for regulating a range where the wafer is mechanically scanned is set to be varied, and, at the same time, a beam scanning speed of the ion beam is changed, in ion implantation at each set angle in a plurality of ion implantation operations during one rotation of the wafer, such that the ions are implanted into the wafer and dose amount non-uniformity in a wafer surface in other semiconductor manufacturing processes is corrected.
According to another aspect of the present invention, an ion implantation method is provided. In the ion implantation method, an ion beam is scanned in a beam scanning direction and a wafer is mechanically scanned in a direction perpendicular to the beam scanning direction so as to implant ions into the wafer. The method comprises setting a wafer rotation angle with respect to the ion beam so as to be varied and setting a wafer scanning region length for regulating a range where the wafer is mechanically scanned so as to be varied. Ion implantation is performed multiple times for a partial region surface from one end side of the wafer to the set wafer scanning region length during one rotation of the wafer at an angle used as a reference of the wafer rotation angle and one or more set angles changed from the angle used as a reference. A combination of variable setting of the wafer scanning region length and change control of the beam scanning speed of the ion beam in ion implantation at each set angle is performed such that the ions are implanted into the wafer and dose amount non-uniformity in a wafer surface in other semiconductor manufacturing processes is corrected.
According to still another aspect of the present invention, an ion implantation apparatus includes a beam scanner scanning an ion beam in a beam scanning direction and a mechanical scanning system mechanically scanning a water in a direction perpendicular to the beam scanning direction and implant ions into the wafer. The apparatus comprises a rotation device that is provided in the mechanical scanning system and varies a wafer rotation angle with respect to the ion beam and a controller that has a function of controlling at least the beam scanner and the mechanical scanning system. The controller controls the rotation device such that a set angle of the wafer rotation angle with respect to the ion beam is changed in a stepwise manner so as to implant ions into the wafer at each set angle, controls the mechanical scanning system such that a wafer scanning region length for regulating a range where the wafer is mechanically scanned is set to be varied, and, at the same time, controls the beam scanner such that a beam scanning speed of the ion beam is changed, in ion implantation at each set angle in a plurality of ion implantation operations during one rotation of the wafer, such that the ions are implanted into the wafer and a dose amount in a direction where the wafer is mechanically scanned is controlled, thereby performing an adjustment of ion implantation amount distribution in a wafer surface.